Vein occlusion occurs as a result of circulatory dysfunction in the central vein or one of its branches.
Epidemiology: Retinal vein occlusion is the second most frequent vascular retinal disorder after diabetic retinopathy. The most frequent underlying systemic disorders are arterial hypertension and diabetes mellitus; the most frequent underlying ocular disorder is glaucoma.
Frequent underlying systemic disorders of retinal vein occlusion include arterial hypertension and diabetes mellitus. Frequent underlying ocular disorders include glaucoma and retinal vasculitis.
Etiology: Occlusion of the central vein of the retina or its branches is frequently due to local thrombosis at sites where sclerotic arteries compress the veins. In central retinal vein occlusion, the thrombus lies at the level of the lamina cribrosa; in branch retinal vein occlusion, it is frequently at an arteriovenous crossing.
Symptoms: Patients only notice a loss of visual acuity if the macula or optic disk are involved.
Diagnostic considerations and findings: Central retinal vein occlusion can be diagnosed where linear or punctiform hemorrhages are seen to occur in all four quadrants of the retina (Fig. 12.18a). Often one will find distended and increasingly meandering veins. In branch retinal vein occlusion, intraretinal hemorrhages will occur in the area of vascular supply; this bleeding may occur in only one quadrant (Fig. 12.18b) or in two quadrants (hemispheric vein occlusion). Cotton-wool spots and retinal or optic-disk edema may also be present (simultaneous retinal and optic-disk edema is also possible). Chronic occlusions may also be accompanied by lipid deposits. One differentiates between non-ischemic and ischemic occlusion depending on the extent of capillary occlusion. Ischemic occlusion is diagnosed with the aid of fluorescein angiography.
Differential diagnosis: Other forms of vascular retinal disease must be excluded, especially diabetic retinopathy. An internist should be consulted to verify or exclude the possible presence of an underlying disorder.
Treatment: In the acute stage of vein occlusion, hematocrit should be reduced to 35-38% by hemodilution. Laser treatment is performed in ischemic occlusion that progresses to neovascularization or rubeosis iridis. Focal laser treatment is performed in branch retinal vein occlusion with macular edema when visual acuity is reduced to 20/40 or less within three months of occlusion.
Prophylaxis: Early diagnosis and prompt treatment of underlying systemic and ocular disorders is important.
Clinical course and prognosis: Visual acuity improves in approximately one-third of all patients, remains unchanged in one-third, and worsens in one-third despite therapy. Complications include preretinal neovascularization, retinal detachment, and rubeosis iridis with angle closure glaucoma.
Retinal vein occlusion.
Retinal vein occlusion.
Fig. 12.18 a Central retinal vein occlusion: intraretinal hemorrhages are visible in every retinal quadrant.
b Occlusion of the two main inferior branches. Bleeding occurs only in the affected areas of the retina in branch retinal vein occlusion.
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